Semiconductor devices have been produced by the steps of coating an inorganic substrate with a photoresist; patterning the photoresist film by exposure to light and subsequent development; etching exposed region of the inorganic substrate using the patterned photoresist film as a mask to form minute circuits; and removing the patterned photoresist film from the inorganic substrate. Alternatively, after forming minute circuits in the same manner as above, the patterned photoresist film is ashed, and then the remaining resist residues are removed from the inorganic substrate.
In advanced integration, beyond the 22 nm node technology, a metal hard mask may be employed to aid in the fabrication of the device architecture. The hard mask is typically composed of Ti or TiN and provides dry etch selectivity and protection for any underlying, relatively sensitive, low-κ dielectric material, especially porous low-κ dielectric material. One disadvantage of this process it that the resulting etch residue can be very difficult to remove as it is composed of relatively insoluble inorganic polymers of TiOxFy. The primary method of removing these polymer compounds has been to use a dilute HF based cleaning formulation. The use of such a dilute HF based cleaning formulation will often result in damage to the sensitive porous low-κ dielectric and any densified silicon dioxide material on or around the low-κ dielectric or at the interface of the TiN and low-κ dielectric which results in delaminating of TiN. In order to prevent the formation of these inorganic residues a polymeric film can be applied to the substrate using a post-etch plasma treatment, such as for example, a CH4 plasma treatment, as described by O. Jourbert, N. Posseme, T. Chevolleau, T. David, M. Damon, UCPSS (September 2010) Ostend, Belgium; Q. T. Le, F. Drieskens, J. F. de Marneffe, T. Conard, m. Lux, H. Struyf, G. Vereecke, UCPSS (September 2010) Ostend, Belgium.; and N. Posseme, R. Bouyssou, T. Chevolleau, T. David, V. Arnal, S. Chhun, C, Monget, E. Richard, D. Galpin, J. Guillan, L. Arnaud, D. Roy, M. Guillermet, J. Ramard, O. Joubert, C. Verove, IITC (2009) Sapporo, Hokkaido, Japan. This polymeric film essentially eliminates the occurrence of the TiOxFy type residue. However, the post etch treatment (PET) polymeric film must be removed after the etch process and before any subsequent metallization can occur.
Porous low-κ dielectric development has progressed significantly in recent years. General definitions of dielectrics include low-κ dielectrics with κ values less than 3.0 and ultra low-κ dielectrics with κ values less than 2.5. Ultra low-κ dielectric materials are highly porous in nature and more susceptible to damage from chemical treatment either by direct attack of the material's structural framework resulting in etching or by chemical penetration into the pores of the material destroying its insulating properties.
There is a therefore a need to provide a cleaning solution for removing PET polymer film and residue while not damaging any underlying dielectric layer, especially low-κ dielectric materials, or metallization of the device. It is particularly desirable to provide a cleaning composition for removing etch/ash residue, photoresist, and PET polymer while not damaging underlying porous low-κ dielectric layer or the metallization, particularly copper and tungsten.
The improved solution must possess the ability to remove polymeric films and residue from the surface, be as benign as possible to copper metal (etch rate <1.0 Å/min), can neither etch nor damage the porous low-κ dielectric (determined by refractive index and κ value shift), and must be compatible with tungsten and titanium nitride.